Separation Of Methyl Acetate And Methanol By Using Ionic Liquids

Methyl acetate and methanol are typical azeotropes in the production of polyvinyl alcohol.The use of traditional distillation methods results in poor separation and high energy consumption.Extractive distillation is commonly used in the industry,but traditional organic solvents which are usually used as extractant are volatile and large amount,so we need to find a new type of extractant.Ionic liquid(IL)can be designed as a green solvent with the characteristics of non-volatile and strong selectivity.Many researchers have proved that the salt effect of ILs can change the relative volatility of methyl acetate and methanol and ILs are suitable as extractant.Aspen Plus software is used to simulate the process of extractive distillation to separate methyl acetate and methanol with water and[MMIM][DMP]as extractant.When water is used as an extractant,the purity and recovery of methyl acetate product are both 95 wt%while methanol purity is only 79 wt%.When[MMIM][DMP]is used as an extractant,the purity and recovery of methyl acetate product are more than 99 wt%while methanol is 96 wt%.IL can be recycled without any loss.It can be seen that the separation of methyl acetate and methanol with[MMIM][DMP]has better effect.In addition,the separation of methyl acetate and methanol by[MMIM][DMP]has reduced energy consumption about 60%compared with that of water,which greatly reduced the cost-recovering of methyl acetate and methanol.Five ILs are synthesized,namely 1,3-dimethylimidazolium dimethylphosphate([MMIM][DMP]),1-ethyl-3-methylimidazolium diethylphosphate([EMIM][DEP]),1-butyl-3-methylimidazolium dibutylphosphate([BMIM][DBP]),1-ethyl-3-methylimidazolium chloride([BMIM][Cl]),1-ethyl-3-methylimidazolium tetrafluoroborate([EMIM][BF4]),and the ILs in methanol are recovered by pervaporation(PV)with polydimethylsiloxane(PDMS)membrane.The influence of different factors on PV performance with PDMS membrane is investigated.The experimental results show that the total flux increases with the increase of temperature and decrease of IL concentration;there are significant differences in total flux between different ILs and the relationship between total flux and five ILs is:[EMIM][BF4]>[BMIM][DBP]>[BMIM][Cl]>[EMIM][DEP]>[MMIM][DMP];the addition of 1 wt%methyl acetate in feed has little effect on total flux.ILs hardly penetrate through PDMS membrane and the separation factor of methanol is approximately infinitely large.PDMS membrane has a good stability for separating ILs from methanol according to the experiment.The separation of methyl acetate and methanol by IL in extraction distillation and PV method for recovering ILs from methanol have broad prospects.